If you are within 0.7 ~ 1m (28 ~ 39.3 in) from the outside tailgate handle, with your smart key in possession, the tailgate will unlock and open when you press the tailgate handle switch.
The hazard warning lights will blink twice to indicate that the tailgate is unlocked.
Also, once the tailgate is opened and then closed, the tailgate will lock automatically.
Kia Niro 2017 (DE HEV) Service Manual: Rear Seat Belt Retractor Repair procedures
Replacement
When installing the belt, be careful not to damage the retractor.
1.
Remove the rear pillar trim.
(Refer to Interior Trim - "Rear Pillar Trim")
2. ...
Kia Niro 2017 (DE HEV) Service Manual: Power Door Mirror Actuator Repair procedures
Inspection
1.
Disconnect the negative (-) battery terminal.
2.
Remove the front door quadrant inner cover (A).
3.
Disconnect the power door mirror connector from the harness.
4. ...